Continuously variable dimmer switch



Sept. 10, 1963 s. l. SLATER commuousm VARIABLE DIMMER SWITCH 3 Sheets-Sheet 1 Filed June 10, 1960 T in. l

|'T:3;I fi m* INVENTOR. SAL/L 51/; 75k

Sept. 101G963 s. 1. SLATER 3,103,618

CONTINUOUSLY VARIABLE DIMMER SWITCH Filed June 10. 1960 s Sheets-Sheet 2 Tic. 64

4 INVENTOR. 7 SAUL 51475? Sept. 10, 1963 Filed June 10, 1960 S. l. SLATER CONTINUOUSLY VARIABLE DIMMER SWITCH 5 Sheets-Sheet 3 102 LOWO um i l I 25 i l I 3 i r N i I LOAD l I i 1 J J INVENTOR SAUL I. SLATER wv 5 a? ATTORNEYS United States Patent 3,103,618 CONTINUOUSLY VARIABLE DIMMER SWITCH Saul I. Slater, Glen Cove, N.Y., assignor to Slater Electnc Inc., Glen Cove, N.Y., a corporation of New York Filed June 10, 1960, Ser. No. 35,298

- 7 Claims. (Cl. 323-22) This invention relates to power control devices, and more particularly to a continuously variable dimmer switch for applications such as lamp dimming and the like.

The present invention includes an improvement on and may be considered a continuation-impart of my copending patent application Serial No. 3,144 for Continuously Variable Dimmer Switch, filed January 18, 1960.

The aforementioned copendi-ng patent application discloses a continuously variable dimmer switch having, in addition to full-o n and-iulhofi positions, :a range oi posi-- tions in which the power supplied to an electrical load device is continuously variable. The dimmer switch is a two terminal switch device which may be directly substituted-for a standard, single-pole, single-throw switch in conventional, domestic electric outlet boxes and the like. Unlike many of the prior art devices utilized for lamp dimming and similar applications, such as variable transformer or auto-transformers, liorexamplc, the af ore said dimmer switch need only be connected into one side of the alternating current supply line to the load. 7 Furthermore, it is of smaller size, lower cost and: is more easily installed. The dimmer switch employs a silicon controlled rectifier which is coupled between the two switch terminals in series with the load device; A time delaycircuit, such as a variable phase shift circuit, for example, is als coupled between the two switch terminals to provide a controllable gating signal -for the gate electrode of the rectifier. By controlling thephase of the gating signal; it-is possible to control the portion of an applied alternating current cycleover which the rectifier conducts, to thereby control the power supplied to the load. The variable phase shift circuit may comprise; serially-coupledcapacitor and variable resistance elements which are connected in parallel circuit with the rectifier across the switch-terminals. The gate elec trode of the controlled rectifier is coupled to the circuit; junction of the capacitance and the variable resistance bymeans of a limiting resistor and a diode, so that a variation in the resistance; of the circuit caused by adjustment of the :var'iable resistance element varies the phase of the voltage-applied to the gate element with respect to the phase of the switch terminal voltage, tothereby vary the power supplied to the load device in a manner somewhat similar to a grid-controlled thyratron. Additionally, the device disclosed in the aforesaid copending patent ap plication may supply full power to the load device or may completely shut oif thepower to the load device by 3,103,618 Patented Sept. 10, 1963 "ice , of mounting a number of switches or other circuit devices in a standard outlet box makes use of a so-called Despand mounting strap which usually permits three such circuit devices to be supported in a single box. When a number of switches are mounted in'this manner, the problem of heat dissipation becomes severe, due t the relatively small heat dissipation area available for each switch. Obviously, the silicon controlled rectifier produces a substantial amount of the heat to be dissipated. However, the variable resistance of the phase shift circuit also contributes to the heat output and, more importantly, also tends to limit the minimum physical size which the switch device may assume.

Accordingly,'it is an object of this invention to provide a power control device which capableof supplying substantial amounts of power to a load device over 'a substantial range of power values and yet which is capable of assuming an extremely small physical size.

It is another object of the present invention to provide a continuously variable light dimming circuit which is in all cases directly substitutable in a circuit which previously employed the customary single pole-single throw switch; that is, the circuit, according to the present invention, may be inserted where access is available to only one of the two lines leading to an electrical device to be controlled by the dimmer switch.

It is a further object of this invention to provide an improved continuously variable dimmer switch of the type dis-closed in my aforementioned copending patent application for controlling electric lamps and thelike, which improved dimmer switch occupies a much smaller physical space without diminishing its power handling capacity. 1

It is a still iurther object of this invention to provide a continuously variable dimmer switch which is of such a compact size as to enable a plurality of such switches to be mounted in a single standard size electric outlet box.

It will be useful to explain generally the advantages provided by' the'circuits described herein compared to that of my prior copending application Serial No. 3,144.

Briefly, for a given amount of load power-handling capacity, the physical size of the continuously variable dimmer switch depends to a large extent upon the size of the variable resistance in the phase'shift circuit for a the silicon con-trolled rectifien. Since, for a given powerduction in physical size is preferably obtained in the phase means of one or moreiswitches whichm ayzbe conveni- 'ently actuated by the same control means used to control the variable resistance'in-the pliase'shift circuit.

While the aboveadescribed continuously variable dimmer switch may be physically constructed to occupy an extremely smallspace, suchas would comfortably fit into a standard electric outlctbox, for example, it is nevertheless desirable to provide such a device which occupies a still smaller space and yet which is capable of handling it is desirablethat electric switch components be made of a small enough physical size to enable two orthree reasonably largeamounts of load power. For example, 7 I

shift circuit. The present invention proposed to accomplish this by the inclusion of a simple, commercially available diode of small size serially coupled in the phase shift circuit with the capacitance and variable resistance. When such a diode is included in the phase shift circuit, the output of the diode which energizes the circuit contains a direct current component and an alternating current or ripple" component. Accordingly, his then pos sible to utilize a variable resistance of a much smaller size it'o provide substantially the same phase shift opera-' tion because of the reduction in the direct power to be handled by the circuit. Additionally, the presence of the diode in series with the phase shift circuit makes it possible to omit the diode previously employedwith the limiting resistor in the input to the gate electrode of the silicon controlled rectifier without danger of damagposed by, the various safety codes. common method ing the rectifier. The improved continuously variable dimmer switch of the invention also includes means for dissipating the heat produced by the silicon controlled rectifier to enable a number of the smaller sized switches rectifiers or to other types of rectifiers.

' to be mounted in a single-loutlet boxjof standard size without exceeding a safe operating temperature;

In the drawings:

FIG. his a schematic circuit diagram of the improved continuously'variable dimmer switch of the present 1n-' vention; v V a FIG, 2 is a front. elevational view of a suitable switch-L plate and'housing for thedirnmer switch of FIG. 1;

FIG. '3 is a side elevational view of the switch plate and 2 housing of, FIG. 2 with a portion of the housing broken away to reveal details of construction;

, FIG. 4 is a sideelevational view of a variable resistance and switch assembly which could be employed in the device of FIG. 1; V a

FIG. 5 is a sectional view taken along the line 5-5? of FIG.-4; V a

FIG. 6 is "a sectional view taken along thezline 6--6 of G- rent; -sign al rather" than. voltage signals;

ode electrode.-

- In operation, the silicon controlled rectifier 16' funce tions to control thepoweroutput; to the load 13 by' varying the portion of the alternatingcurrent cycle applied: to terminals1112 over which the rectifier conducts. As

explained in. more detail in the aforementioned copending patent application, a time delay circuit, which may comprise aphase shift circuit, for examplais employed 7 to control the point in, the cycle of applied line voltage at which the rectifier 1 6'conducts and therefore controls the power applied to the 1o'ad13; To this end, switch terminal FIG. 7 is'a front elevational view showing three of the improved continuously variable dimmer switchesof the present invention mounted in let box; f. I 1 I FIG. 8 is a schematic circuit diagrarnl of all-alternative form of variable dimmer switch according to the present invention; and

I f FIG. 9 is a schematiccircuit diagram of a further alternative form of continuously variabledimmer switch according to the present invention. 7

Referring now to FIG. 1' of the drawings, there is shown .'a continuously variable'dimmer switch 10 constructed in accordance'with the teachings of the present invention a standard size electric outswitch terminals 11 and 12 by. means of'leads'21, 3'2, 33 '2 and having two switch terminals -11-and 12. The switch 10 is connected by the terminals '11 and 12 in series cirof a source of alternating voltage, which may, for example, be'the conventional 115 volt, 60 cycle household powersupplyr In accordance with the usual Wiring practice, the'supply terminal 15 may be grounded, so that the'switch 10'is connected in the hot side'of the load a supply line. The load 13 may comprise one, or. more incandescent lamps or certain types of other equipment,

- such as heaters or motors, for example. Since the dim- 'mer switch provides a half-wave output having a direct current componenL-load devices suitable: only foralter- 1 natingcurrent 'operation may notbe employed; It will be noted that the switch 10 is a two terminal device having terminals 11 and 12, so thatit needbeconnectedin only one side of'the line supplying the load 13. This is quite important; since it permits the dimmer, switchof the invention to be directly substituted for the usual,

, single-pole; sing1e-throwswitch. customarily employed The -usual: types .of dimmer arrangemenn suohas those' utilizing. variabletransformers or auto-transformers, for example, 1 I require that the dimmer device'be connected into both sides of the power supplyline, with the result that these" devices cannotbe wired into the usual household circuits without expensive alterations. The, dimmer switch itself comprises a silicon: controlledrectifier 16 having an anode in household and other sirnilar applications.

electrode 17, a cathode electrodelS, and agate electrode rectifier 16 is a PNPN semi-conductor device which operates infa manner similar to a gridac'ontrolled thyratron.

- The reverse current blocking characteristic of the silicon controlled rectifier'is generally-similar to that of silicon However, the forward current in the silicon controlledrectifier is controlled by a gating signal which is applied to the gating electrode '19 to institute or start forward conduction.

Similar to the thyratromthe silicon controlled rectifier continues to conduct in a forward direction once conduction has bee n started, even after the gating signal has been removed. Unlike the thyratron, however, the gating or control'signal for the rectifier is essentially a cur- I cuit with a load device 13 and the terminals 14 and 15 very low gate current, to thereby permit the values of the other circuit elements to be standardized. Accordingly, A i

. resistor 38 may be omitted, if desired, so that the; potential 11 is coupled by means of a lead 2 1, a diode 22, a variable i resistance-switch assembly 23, a capacitor 24 and a lead 25' f to the switch terminal 12. The variableresistance-switch assembly 23 comprises. a variable resistance 26 having a movable wiper arm 27 and a pair of'switches 28' -ands29; Leads 30 and 31 serve toconnect switch 28 in seriescir f cuit'with the wiper arm 27 of the variable resistance and a the capacitor, The-switch 29* is connected in parallel with the silicon controlled rectifier 16 directly across the and 25. The wiper arm 27 of thevariable resistance and thejm'ovable contacts of the switches 28-and 29 are mechanically interconnected as indicated schematically by the dottedline 34, so that these elements may be;

operated in a predetermined sequence by rotation of a control knob 35, as will be more fully explained hereinafter. 'The circuitjunction of capacitor 24- and variable resistance 26 is connected to the gate electrode 19 of the silicon controlled rectifier- 16 by means of a limiting resist-J mice '36 and a lead 37. The gateelectrode 19 is also connected to the cathode electrode 18 of the rectifier-through lead 37, an adjusting resistor 38 and leads 25 and 20 Resistor38 is employed to compensate for the variations in gate current encountered during a normal production, run of the silicon controlled rectifier. Since, in a normal production run of such rectifierspthe gate or trigger current varies widely from rectifier to rectifier, theresistor g 3'8'may be used to desensitize those rectifiers havingra atthe gate electrode .19i'iS essentially the same asthe formalvariable time delay or phase shift circuit in which the voltage appearing at the circuit junction of capacitor: .24 and resistance 26 is of variable phase with; respect to potential at the circuit junction of capacitor Mend vari-i V able resistance26. Finallyiza capacitor 39 is shunted di-'v reotly across the controlled rectifier 16 and the'switch terminals 11, and 12 by means of a lead 4(lto minimize any interferencewith radio or television equipment which mightbe produced by the operation. eithe switch. I

In operation, capacitorj'24 and variable resistance 26 the phase of the voltage appearing. at'terminal 11 01 the v 460 '19 and. 1s serially connectedbetween'the switch ter minals. 11 and'12' by a lead 21);v The silicon controlled 1 resistance will lag the phase of the voltage appearing at switch terminal 11 by an amount generally proportional a to the amount of resistance provided by the variable resistance 26. Since the phase of the'voltage at the circuit junction of capacitor 24 and variable resistance. 26 determines the phase of the gating signal applied to gate electrode 19 0f the silicon controlled rectifier 16, it 'determines the. point on the' applied cycle 'ofsupply voltage at whichthe rectifier begins .forward conduction andtherei 7 Usually, in orderto drive the rectifier into forward conduction, the gate electrode is biased. positive witlr respect, to the cathfore determines the power output passed by the rectifier to the load 13. Accordingly, by actuating control knob 35 to, vary resistance 26, it is possible to control the power supplied to load 13. Since the diode 22 is in series circuit with the variable resistance 26 and the capacitor 24, the energizing source for the phase shift circuit will supply half-wave, pulsating direct current having a direct current component and an alternating current or ripple component of the same frequency as the line voltage at input terminals 14 and 15. By utilizing a half-wave rectifier or diode, the power that the variable resistance 26 must handle is very greatly reduced, so that it is possible to employ a variable resistance of greatly reduced physical size. It will be noted, of course, that the diode 22 still permits the required phase shift control for the controlled rectifier 16-, since the capacitor 24 still is charged with a delay controllable byvariable resistance 26. Furthermore, itis no longer necessary to employ a diode in lead 37 for the gate electrode 19, as in the dimmer switch of my aforementioned copending patent application, to assure that the gate control current will be of the. correct polarity to prevent damage to the rectifier 16.

By suitably arranging the operating sequence of variable resistance 26 and switches 28 and 29 of the variable resistance-switch assembly 23, it is possible to apply full power or to completely shut off power to the load 13 in addition to providing a'range of continuously controlled power. This may be accomplished by causing the mechanical. interconnection 34 to maintain both switches 28 and 29in an opened condition and the wiper arm 27 at the full resistance position of variable resistance 26 when the control knob 35 is in an ofi position, for example, at the extreme counterclockwise position of its range of rotation; At this time, the only direct connection to the load-13 from the input terminal 14 is through the silicon controlled rectifier 16. However, the rectifier is prevented from conducting because switch 28 is opened in the phase shift circuit. Asthe knob 35 is rotated in a clockwise direction, switch 28 is arranged to close and. switch 29 remains open, so that the phaseshift circuit becomes operable to control the conducting .point of rectifier 16. As the knob 35 is rotated, less and less resistance is provided in the phase shift circuit by the variable resistance 26, so that the rectifier 16 conducts at points closer and. closer to the start of the cycle of supply voltage; Therefore, the power supplied to load 13- gradually increases with clockrotation of knob 35 until the variable resistance '26 is.completely shorted out At this time, the mechanical interconnection 34 is arranged to close switch 29' to bypass rectifier. 16 and thereby directly connect the load 13 across the input terminals 14 and 15. This full-on position, of course, applies full line voltage and 'power to thefload. While continuous variability is not provided throughout the range from off to full 'po'wer in the circuit of FIG. 1, the continuously variable range is particularly efiective as: a practical matter, when the switch is used in conjunction with incandescent lamps.

At low powers, incandescent lamps have a marked 'drop in efliciency for the production of visible light, so that the variable dimmer switch readily'allows the dimming of an incandescent lamp until its light output is about Zpercent Of its maximum value. It is believed, apparent that further dimming'would be of relatively little value in the usual household application. When'the dimmer switch ofthe invention is employed in household or similar applications, the capacitor 39 may be utilized as shown to shunt the rectifier 16 to minimize the effects of spurious frequencies produced by the rectifying action on radio and television sets and the like. i

A FlG. 2 of the drawings illustrates the improved dimmer switch of the invention mounted .on a switch plate '50. The control knob 35 of the variable resistance-switch assembly 23' is provided with a pointer 51 which cooperates with an fOif position marking 52 and a Bright electric outlet box. The variable resistance-switch assembly 23 is arranged to be controlled by the knob by means of a single shaft 56. The silicon controlled rectifier 16 is mounted on a support plate 57 by means of a nut 58, so that the rectifier envelope maintains a good physical contact with the plate to enable good heat conduction to take place. The plate 57 is preferably made of copper or other material having good heat conductivity and extends along the rear and the two side walls of the housing 54 in close physical contact therewith. By virtue of this arrangement, the heat produced by the rectifier 16 is conducted alongthe plate 57 which forms a heat sink in the manner described in my copending patent application, Serial No. 5,000, filed January 27, '1960, forLight DimmingSwitch, now Patent No. 3,037,146, and is then transferred through the walls of the housing 54 over a broad area to enable it"to be readily dissipated If desired, an additional heat sink in the form of U-shap ed plate 59 maybe employed around the outside walls of the housing 54, as illustrated, to further aid in dissipating the heat generated bythe rectifier 16. Furthermore, the additional heat sink 59 may be soldered to the mounting strap for the switch to provide a still further increase in heat dissipating area for the switch. The switch terminals 11 and 12 may be brought out through openings (not shown) formed in the top and bottom walls of housing 54 to facilitate the making of connections to'existinghouse wiring. The remainder of the components for the dimmer switch, including diode 22, capacitors Hand 39, and resistors 36 and 38 may be conveniently positioned in any space available in the housing 54 by supporting them directly on the wireleads to the componentsor by-seating them in openings formed in the housing itself.

The structural details of a suitable mechanical arrangement for the variable resistance-switch assembly 23' of the dimmer switch are shown in FIGS. 4-6 of the drawings- As seen in FIG. 4, the assembly comprises a variable resistance portion 60, which may bee. simplevariable resistor of the type utilized in radio and television' receiving sets, for example, and a switch portion 61 which is directly mounted on the housing of the variable resist V ance portion 60. The variable resistor 60 is actuated by rotation of control shaft 56 which is seated in a threaded sleeve 62 having a mounting nut 63 thereon. .When the assembly is placed in the housing 54 of the switch, it may be secured tothe front 'portion'of thehousing by means of the threaded sleeve 62 and the mounting nut'63'. The terminals forthe potentiometer 60 are indicated generally at 64 and the. terminals for the switch portion 61 'areindicated generally at 65. As seen in FIG. 5 of the drawings, the switch portion 61 is a substantially separate unit which is actuated by an extended, flattened portion '66 of the control shaft 56. The shaft portion '66 has mounted thereon a pair of cams 67 and 68- which respectively control the switches 29 and 28. Carn 67 is arranged to actu ate 'switch 2? by means of 'a cam-follower projection 69 formed on the movable switch'arm 70 of 'the switch 29 A recessed portion 71 is formed in the outer peripheral edge of thecam 67 to cooperate with the follower projec' tion 69 when the control knob 35 is in the full-on or Bright position to close switch 29. Accordingly, for all positions of knob 35 otherthan the Brighf position, the switch 29 remains open. The cam 68 cooperates with a cam-follower projection 72 formed on the movable switch arm 73 of switch 28. A projection 74 is formed on cam 68 and is arranged to engage the follower projecpotentiometer) andthe cams-67 and 68 of the switch portion simultaneously, it is apparent that a single control a operatedflby rotation of knob 35 is provided to. place the switch in any'of its desired positions. :Accordingly, ;the

lamp or lamps forming the load for the dimmer switch of the invention may be turned, completelyoif, or on to I full brightness, or may be dimmed over a continuously variable range, all by means ofa single operating control. 1

Byemploying the diode 22, which may be a semiconductor,-for example, in the phase shift circuit for the silicon controlled rectifier, it is possible to materially reduce the size of the variable resistance portion 60 of the variable resistance switch assembly 23; to thereby greatlyreduce the overall physical size of the dimmer, switch. As shown in FIG. 7 of the drawings, this permits a number of g dimmer switchesto be mounted in a single, standard size,

electric outlet box 80.. The three dimmer switches 10, constructed in accordance with the teachings of .the presentinvention, are supported in the outlet box by. means of a mounting strap 81 which is secured to the box by screws. 82. The strap 81 may be of the Despard type,

or may comprise any other convenient mounting arrange ment as known in. this art. Each of the dimmer switches 10 is. secured to a separate, interchangeable mounting f plate 83, which engages the projections 55 formed on the housing 54 of each switch and the'mounting plates are,

in turn, secured to the mounting strap 81.

Suitable circuit values for the dimmer switch shown in FIG..1 of the drawings for use with a silicon controlled rectifier, such as a General Electric Co. Type C3613, for

example, are given by way of, illustration as tollows:

' Variable resistance 26-1 00 ,O0() ohms, approximately watt. Capacitor 24--.5 mf.,' 25 volt D.C.

I Capacitor 39-'-.25 mf.', 200 volt A.C.

Resistor 36-7500 ohms. I Resistor 38-1 00 ohms and largerdepending upon the gate current characteristic of the particular silicon controlled rectifier employed. 1 e a As hereinbefore' explained, while continuous variability ,is not provided throughout the entire range from off to full power, the dimmer switch of the invention is particuw larly efiective for controlling incandescent lamps over a range of, forlexample, 2% to of their rated light output. It may be noted that by the addition of an oppositely polarizeddiode in parallel with the silicon controfled rectifier lfiandjappropriate switching, the range of power from 50 to 100% could be provided with substantially continuous-control.

Such an alternative form of circuit a 'diodc rectia tier in parallel is shown in FIG; '8. The circuit of FIG. 8

" includes the elements of the circuit of FIG. 1 and, in addition, a parallel'circuit is'provided between terminals 11 and 12 comprising a diode rectifier 102 polarized oppositely to the silicon controlled rectifier 16. In series with the diode rectifier 102, is a single-pole, single-throw switch When the switch 101 is moved to the position marked ously variable dimmer switch is substantially as explained with reference to FIG. Land gives a continuously variable range of power between. zero and fifty percent of .full

power; When-switch 101 is moved to the position marked High? and the parallel oircuit'is completed, it

trolled rectifiericircuit will theny-ield a rangeof continu ously variable power between the values of fifty percent and one hundred percent full power.

Switch 29* and leads 32 and 33 to provide full power in FIG. 1 will generally be unnecessary in the circuit of 7 FIG. 8, but may be retained and will provide the inci-' dental advantage-of relieving the load from the diode and silicon controlled. rectifier during full power operation; Additionally, it is possible to employ, two T or the dimmer switches 10 .of the invention in parallelcirouit, but with opposite polarity, to give continuous powercone trol above 50% or run power. This arrangement also has the added advantage of permitting the controls of the two dimmer circuits to be gauged together to reduce the aver age current to the load to zero, so thatno substantial directcurrent componenrwould exist to. damage those load devices whichlare for energizationby alternatingcurrent only. r n Such an alternative 'tfo-rm cfdouble dimmer circuit arrangement is illustrated in FIG. 9, wherein the circuitry a shown in the enclosure '11 of FIG. 1 is retained and substantially duplicated in FIG. 9, except that capacitor39, leads 40, leads 32 and 33, and switch 29Mare' not duplicated; i as such duplicate elements obviously would be superfine oust 7 In FIG. 9, elementsrare given the Same reference nu merals as in FIG. 1, except for the addition of the suflix a and the suffix b in the case of retained and duplicated elements, respectively. Elements in the FIG. 9 circuit retained from the FIG. circuit operate in the same manner, already explained with reference to FIG. 1. Duplicated elements in FIG. 9*also operate in a manner similar to the FIG. 1 circuitexcept that it will be noted that silicon controlled rectifier 16b,

in FIG. 9 is, connected withits associatedcircuitry be; tween terminalsll and 12 so that it is oppositely polarized with respect to the silicon controlled rectifier 160. Thus each of the silicon controlled rectifier-s operates SHlbSiall'. i

tially independently on opposite halves of the alternating current wave formation, and the range or continuous adjustm'ent in terms of percentage. of toll power is doubled. t r

Usually it 'willbe desiralble to gang together thejcontrols, V as indicated bylthe dashed line in FIG. *6, in order that dull-range control may be obtained with a single control.

This also substantially eliminates any tdirectscurrent com.- ponent through the load circuit, as previously. explained.

It is believed apparent; that many changes could be made in the above construction and many apparently widely different embodiments of this. invention could be 'made without departing fro'm the scope thereof; Forexample, other, similar devices could be substituted tor the silicon controlled rectifier 16, and the half-wave diode i 22' could 'be replaced by other types'of rectifiers. .Addi' tionally, other physical forms lior the variable resistancep switch assembly 23 could be utilized and other arrange ments of the component parts of the switch could be em,-

I, ployed it. desired. Accordingly it is intended that Low? to openthe circuit, the-operation of the cont-inuwill be noted'that. one-half of the alternating current wave form will be shunted around the silicon controlled rectifier 16, and the controllable power will be fitty '7 percent of the-full power. Adjustment of the silicon conmatter contained in the above: description or shown the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1'. A power control and switch device providing sub stantially continuous controlof power supplied to aload over a'substantial range of power 'valuescornprising two terminals for connecting said device in series in one side of the two sides of the power line [from an alternating I current power source supplying current to .the load,a recti-' tier element having a cathode, anode and gating electrode; 4

a switch, means connecting said rectifier element betweensaid terminals to cause said rectifier element to be con I: nected by means of its cathode and anode terminals series between said two terminals, means connecting said switch between said two terminals to selectively provide a separateelectrical path betweengsa'id two terminals, and a to initiate conduction by said rectifier element at instants of time bearing a controllable relation with respect to the beginning of alternating current cycles or power available at said two terminals, whereby a portion of each alternating current cycle, which portion is continuously controllable in duration over a predetermined range, may be supplied to the load connected in; circuit with said device. 1

2. Apparatus as claimed in claim 1 wherein said rectifier element is a controlled rectifier and further including a further rectifier element and means for connecting the last said rectifier element in shunt betweensaid two terminals with its polarization opposite to that of said controlled rectifier.

3. Apparatus as claimed in claim 1 further including a secondary circuit substantially the duplicate of that of said device of claim 1, said secondary circuit being connected in shunt between said two terminals with its polarization opposite to that of the said rectifier of claim 1.

4. A power control device as claimed in claim 1, further comprising a housing and a member for mounting said rectifier'element, said member being formed of a good heat conducting material and extending along at least a' portion of the walls of said housing interiorly thereof, so that said member acts as a heat sink to dissipate the heatproduced by said rectifier.

5. A power control device providing substantially continuous control of power supplied to a load over asubstantial range of power values, comprising two terminals for connecting said device in series circuit in one side of the two sides of a power line supplying current to the load; a control-rectifier having the anode and cathode electrodes thereof serially coupled between said terminal's, said rectifier being of the type having a gate electrode in addition to said anode and cathode electrodes said capacitor from one to the other of said terminals, 'whereby said delay circuit is adapted tocontrol the portion of an alternating current cycle applied to saidterminals over which said rectifier conduct-s to thereby control the power applied to the load.

6. A power control and swit'chdevice providing substantially continuous control of power supplied to a load 'over a substantial range of power values comprising two terminals for connecting said device in series in one side of the two sides ofthe power line from an alternating current powersource supplying current to the load, a semiconductor control element having first and second electrodes, said control element normally being substantially non-conductive between said first and second electrodes and being adapted to be rendered conductive in at least one direction by a control signal, means connecting said control element in series between said two terminals by means of its first and second electrodes, and a variable time delay means energized from said two terminals for providing a control signal to said control element, said control signal being controllable to initiate conduction by said control element at instants of time bearing a control lable relation with respect to alternating current cycles of power available at said two terminals, whereby portions of alternating current cycles, which portions are continuously controllable in duration over a predetermined range, may be supplied to the load connected in circuit with said device.

7. A power control and switch device providing substantially continuous control of power supplied to a load over a substantial range of power values comprising two terminals for connecting said device in series in one side of the two sides of the power line from an alternating current power source supplying current to the load, a semiconductor control element having first and second electrodes, said control element normally being substantially non'conductive between said first and second electrodes and being adapted to be rendered conductive in at least one direction by a control signal, means connecting said control element in series between said two terminals by means of its first and second electrodes, a variable time delay means energized from said two terminals for providing said control signal to said control element, a switch and means connecting said switch to selectively open the circuit for said control signal between one. of said terminals and said control element,

said control signal being controllable by said time delay' means to initiate conduction by said control element at instants of time bearing a controllable relation with respect to alternating current cycles of power available at said two terminals, whereby portions of alternating current cycles, which portions are continuously controllable 1n duration over a predetermined range, may be supplied to the load connected in circuit with said device.

References Cited in the file of this patent UNITED STATES PATENTS 2,920,240 Maoklem Jan. 5, 1960 

1. A POWER CONTROL AND SWITCH DEVICE PROVIDING SUBSTANTIALLY CONTINUOUS CONTROL OF POWER SUPPLIED TO A LOAD OVER A SUBSTANTIAL RANGE OF POWER VALUES COMPRISING TWO TERMINALS FOR CONNECTING SAID DEVICE IN SERIES IN ONE SIDE OF THE TWO SIDES OF THE POWER LINE FROM AN ALTERNATING CURRENT POWER SOURCE SUPPLYING CURRENT TO THE LOAD, A RECTIFIER ELEMENT HAVING A CATHODE, ANODE AND GATING ELECTRODE, A SWITCH, MEANS CONNECTING SAID RECTIFIER ELEMENT BETWEEN SAID TERMINALS TO CAUSE SAID RECTIFIER ELEMENT TO BE CONNECTED BY MEANS OF ITS CATHODE AND ANODE TERMINALS IN SERIES BETWEEN SAID TWO TERMINALS, MEANS CONNECTING SAID SWITCH BETWEEN SAID TWO TERMINALS TO SELECTIVELY PROVIDE A SEPARATE ELECTRICAL PATH BETWEEN SAID TWO TERMINALS, AND A 